Apple today posted an updated security document [PDF] on its iPhone in Business site, offering details on the inner workings of both Touch ID and the "Secure Enclave" built into Apple's A7 processor (via TechCrunch). Since its 2013 release, Touch ID has faced scrutiny over privacy concerns from both users and government officials, and while Apple has previously offered few details on how Secure Enclave works, it has assured users that the system stores only fingerprint data rather than images.